446 BLEININGER AND BROWN! VERITOS FIRING RINGS 



younger sets of moraines are similar to each other, in forms and 

 relations, but show important differences in the effects of subse- 

 quent erosion and weathering. The probable relations of the 

 glacial stages to the erosional cycles are discussed. The activity 

 of the wind in sculpture and deposition has been important. 

 Interesting phenomena of gravity work, in the form of land-slides, 

 earth-flows, and talus-glaciers receive brief mention. 



TECHNOLOGY. — The veritos firing rings. A. V. Bleininger 

 and G, H. Brown, ^ Bureau of Standards. Communicated 

 by S. W. Stratton. 



In the pottery and other clay industries the heat effect due 

 to the increasing kiln temperature is frequently determined from 

 the shrinkage of unburned clay rings, of uniform composition 

 and size, which are placed in different parts of the kiln. The 

 shrinkage is measured by means of a simple calipering device 

 which permits the reading of small differences in diameter. The 

 object of the present work was the correlation of the arbitrary 

 shrinkage number of the gauge with temperature as measured 

 by means of standardized thermo-couples, so that the devices 

 might be coordinated with pyrometer practice. 



The work consisted in firing a number of these rings under 

 conditions of constant temperature increase per unit time. Four 

 firings were made with increases in temperature of 50, 25, 16.66 

 , and 12.5°C. per hour. At frequent intervals rings were with- 

 drawn from the kiln and their diameters measured after cooling. 

 The temperatures at which equal contraction takes place are 

 higher the more rapid the firing. The differences diminish as 

 the temperature rises. The shrinkages for the two lower firing 

 rates tend to coincide as the heat absorption becomes constant. 

 Porosity determinations were made in connection with the shrink- 

 age measurements; these resulted in curves practically parallel 

 to the linear contraction. The firing rings were found to answer 

 the purposes for which they are intended satisfactorily. A new 

 series of rings, intended for lower temperatures, was found to 

 be unsatisfactory, owing to irregularities in shrinkage. 



• To appear as Technologic Paper No. 40 of the Bureau of Standards. 



